Hydraulic valve systems, whether completely sealed or not, rely on calibrated input control for the positioning of the valve and control of flow rate and the like. The input control is generally mechanical or electro-mechanical in nature. Accordingly, relatively large deviations from the desired valve position and flow rate are inevitable. Even fully electronic controls do not overcome such deviations, because of the mechanical nature of the valves involved, as well as the constantly varying hydraulic pressures used in the actuation of the valve or valves.